Strap tensioning and locking tool



April 15, 1969 w. J. ROZMUS STRAP TENSIONING AND LOCKING TOOL Filed Oct.13, 1966 INVENTOR. 14 4/2 62" J7 fiazmrzzs.

emvzvf BY g April 15, 1969 w. J. ROZMUS STRAP TENSIONING AND LOCKINGTOOL Z of 3 INVENTOR. 97%:27zzzs Sheet April 15, 1969 w. J. ROZMUS $TRAP TENSIONING AND LOCKING TOOL INVENTOR. M/Zir J 2 0127045.

BY w 9% I7 0 United States Patent 0 3,438,406 STRAP TENSIONING ANDLOCKING TOOL Walter J. Rozmus, Hubhardsville, N.Y., assignor, by mesneassignments, to Utica Tool Company, Inc., Orangeburg, S.C., acorporation of Delaware Filed Oct. 13, 1966, Ser. No. 586,561 Int. Cl.1521f 9/02, 45/16 US. Cl. 140--93.2 21 Claims ABSTRACT OF THE DISCLOSUREA power operated strap tensioning tool in which a serrated roller iscontinuously driven in rotation. By pulling a trigger the end of thestrap to be tensioned is biased against this roller so that the rollerwill grip it and tighten it. When a predetermined tensional loading isapplied to the strap a spring will yield so that the power used to drivethe roller is employed to produce rotation of a strap supporting memberto impart a permanent twist to the tensioned end of the strap andthereby lock the strap in the tensioned position.

This invention relates to a tool for applying a tensioned strap around abundle of wires, or the like, and more particularly to a power tool thatwill upon the occurrence of a predetermined tension in the strap, twistthe strap and thereafter cut it on the side of the twist remote from thebundle of wires or the like to provide a permanent tie for the bundle ofwires or the like.

In accordance with the present invention, there is provided a poweroperated tool for tensioning a strap about a bundle of wires which maytake the form of a group of electrical insulated conductors that arearranged generally parallel to one another. This grouping of wires iscommonplace in various structures, such as, automobiles, airplanes andother vehicles in which a plurality of electrical circuits must beoperated at a place remote from circuit-actuating means. These wires arecommonly grouped together in a parallel fashion and are carried by thestructure in which they are mounted by various fastening means thatattach them to the structure in which they are mounted. It is desirablein these circumstances, to provide some means for tying the parallelwires together to form a simulated cable member that may be readilyhandled and threaded through a structure in which the conductors areused.

The present invention provides a tool for tying these parallel extendingwires or conductors together to form a simulated cable. The tool ispower operated and comprises a first jaw means for restraining movementof one end of a strap which has been positioned about a plurality ofconductors and a second jaw means for gripping the other end of thestrap which has been positioned through an aperture in the first end.Means are coupled to the second jaw means for driving the second jawmeans to tension the strap, and means are provided responsive to apredetermined tension in the strap for twisting the portion of the strapheld by the second jaw means to impart a permanent twist to the strap.Means are also provided for shearing or cutting the portion of the strapon the opposite side of the permanent twist from the end portion thereofwhich has the above-mentioned aperture positioned therein upon thecontinued twisting of strap.

An object of the present invention is the provision of 3,438,406Patented Apr. 15, 1969 a novel power-operated tool for tensioning andsecuring a strap about a parallel group of conductors, wires or thelike.

Another object of the invention is the provision of a power operatedtool that will automatically tension a strap positioned about a group ofconductors, wires or the like, twist the strap upon a predeterminedtension existing in the strap and thereafter shear the strap in aposition remote from the twist with respect to the bundle of wires sothat the strap is permanently secured in a tensioned condition about thebundle of conductors, wires or the like.

Another object of the invention is the provision of a power-operatedtool which will tension a strap positioned about a parallel group ofconductors, wires or the like and will thereafter impart a permanenttwist in response to a predetermined tension in the strap to therebypermanently place the strap in a tension condition about the group ofconductors, wires or the like.

Other objects and attendant advantages of the present invention may bemore readily realized as the attached drawings are considered inconnection with the specification in which:

FIGURE 1 is a top plan view of the power-operated tool of the presentinvention;

FIG. 2 is a front elevational view of the power operated tool of thepresent invention;

FIG. 3 is a longitudinal sectional view taken along the lines 33 of FIG.1;

FIG. 4 is a partial longitudinal sectional view similar to that of FIG.3 and showing the power-operated tool in one phase of its operation;

FIG. 5 is a partial longitudinal sectional view similar to that of FIG.3 and showing the power-operated tool in another phase of its operation;

FIG. 6 is a partial sectional view taken along the lines 66 of FIG. 1;

FIG. 7 is a sectional view taken along the lines 7--7 of FIG. 3;

FIG. 8 is a view taken in the direction of the arrow of FIG. 3;

FIG. 9 is a view taken along the lines 9-9 of FIG. 3;

FIG. 10 is a sectional view taken along the lines 1010 of FIG. 5;

FIG. 11 is a sectional view taken along the lines 1111 of FIG. 1; and

FIG. 12 is a view similar to FIG. 11, but showing the power-operatedtool in a different phase of its operation.

Referring now to the drawings, the power-operated tool 10 of the presentinvention is shown generally in FIGS. 1 and 2 and it comprises a housing11 having a generally cylindrical rear housing portion 12, a fronthousing portion 13 and a handle 14. The end 16 of the front housingportion 13 of the power tool has a longitudinally extending slot 18positioned in an end wall 20. An oblong depression 22 is positionedaround the slot 18 for the reception of an enlarged end portion 24 of astrap 26 positioned around a group of parallel extending wires,conductors or the like, generally designated by the numeral 28, as canbest be seen by reference to FIG. 4. The other end 30 of the strap ispositioned through an aperture in the enlarged end portion 24 and thenceinto a position to be engaged by a serrated roller 32, as will bedescribed subsequently.

As can best be seen by reference to FIG. 7, the serrated roller 32 has agroove 34 extending circumferentially thereof, and it is integrallyformed with a gear 36 and a helically grooved guide 38. The gear 36 isrotatably positioned in a bore '40 of a support member 42 and thesupport member 42 is afiixed to a longitudinally extending cylinder orbarrel 44 by any suitable fastening means. The support member 42 and thecylinder 44 are rotatably supported in the housing 11 for rotation aboutan axis passing through the center of the cylinder 44 by means of anannular groove 46 positioned in the rear housing portion 12 whichrotatably receives the end of the cylinder remote from the supportmember 42 and by a bore positioned in the end of the front housingportion 13 that receives a reduced cylindrical portion 50 formed on thesupport member 42.

Referring now to FIG. 6, the gear 36 is driven by a Worm 52 rotatablysupported in the support member 42 along an axis parallel to the axis ofthe cylinder 4'4 and perpendicular to the axis of the gear. This worm 52has an enlarged extension 54 connected to a flexible drive cable 56, andthe flexible drive cable is also attached to a driving means 58 thatincludes a clutch 60 (see FIG. 3). This drive means includes acylindrical drive sleeve 62 rotatably supported in the rear housingportion 12 by means of a radial bearing 64. The driven cylindricalsleeve '62 is attached to a drive cable 66 by means of a threadedenlarged end 68 that is threaded into an internal bore 70 in the sleeveand that engages an adjustable plug 72 that is also threaded in thethreaded bore 70. This adjustable plug 72 engages one end of a helicalspring 74, the other end of which engages a ball 76 for forcing the ballinto engagement with the end of a plunger 78 mounted in an internal borein an extension 80 of the drive sleeve 62. This plunger 78 has a reducedportion 82 connected to its main body 84 by a conical ramp 86.

The extension 88 of the drive sleeve 62 has helical grooves 88 and 90positioned therein, and a differential housing 89 positioned over theend of the main body portion 84 of the plunger 78 has a pair of opposedlongitudinal grooves 92 and 94 positioned therein. The helical grooves88 and 90 are positioned in opposed relationship and receive the ends ofa pin 96, while the grooves 92 and 94 that are also positioned inopposed relationship receive the ends of a pin 98. Each of the pins 96and 98 pass through and is aflixed to the main body portion 84 of theplunger 78.

The drive sleeve 62 has a plurality of apertures designated by thenumeral 100 and each of them receives a ball 102. The halls 102 togetherwith the reduced portion 82, the conical portion 86 of the plunger 84,and an outer clutch ring 103 attached to the cylinder 44 form the clutchdevice 60, as will be explained subsequently.

The handle 14 of the power-operated tool is attached to the rear housingportion 12 by a suitable fastening means, for example, machine screws,one of which is shown at 108 and to the front housing portion 13 byother suitable fastening means, for example, by means of machine bolts,one of which is shown at 111.

A trigger 112 is pivotally positioned in a space 114 in the handle 14 bymeans of a pin 116, and it has a knob '118 positioned thereon oppositethe pivot pin 116 from the end 120 that is adapted to be operated by thetool operator. This trigger 112 is biased into the position shown bymeans of a helical spring 122, as can be seen most readily by referenceto FIG. 3. The knob 118 is suitably positioned in an aperture 124 in aslidable actuating member 126 that has an end 128 in engagement with aspring-urged pawl 130 that is spring-urged into the position shown inFIG. 3 by a coiled spring 132. The pawl 130 has a serrated portion 1'34and a cylindrical or curved portion 136 positioned on the end thereofadjacent the serrated roller 32. The pawl 130 carries a strap positioner140 by means of a pin 142 and it is biased into the position shown inFIG. 8 by means of spring 144.

The handle 14 has an elongated bore 1'50 positioned therein that isgenerally parallel to the cylinder 44 and the axis of the drive means58. This elongated bore has a cylindrical plunger 152 positioned thereinspring-urged by a helical return spring 154 into the position shown inFIG. 3. The compressive forces on the spring 154 may be adjusted bymeans of an adjusting screw 156 positioned in the end of the bore 150.The plunger 152 has an indentation 160 for the reception of a ball 162that is urged into position by a spring 164. The spring 164 ispositioned together with the ball 162 in a sleeve 166 that in return isreceived in a bore 168 in the handle 14. The compressive force on thespring 164 may be adjusted by an adjusting screw 170. The plunger 152carries a pin 172 having a roller 174 positioned thereon that isreceived in a helical groove 176 positioned in the cylinder 44, as canbest be seen by reference to FIG. 9.

Referring now to FIGS. 10-12, the reduced cylindrical portion 50 of therotatable support member 42 has a radially extending slot 190 positionedtherein that is aligned with the slot 18 in the end 16 of the fronthousing portion 13 when the tool is in its unactuated position as shownin FIGS. 2 and 3 and 11. A shearing knife 192 is pivotally mounted onthe reduced portion 50 of the rotatable support member 42 adjacent slot190 by means of a pin 194.

During the operation of the power-operated tool of the presentinvention, the strap 26 is positioned around a group of parallelextending conductors, wires or the like 28 and the end 30 which issubstantially rectangular in cross section, is positioned through acomplementary rectangular slot in the head 24 of the strap 26. The end30 is then positioned in the tool through the slots 18 and 190 and thispositioning is best shown in FIGS. 3 and 11. The end of the strap 30will come into engagement with the serrated roller 32 and this may beaccomplished readily, if there is any misalignment, by means of thestrap positioner shown in FIG. 8 upon the actuation of the trigger 112from its position shown in FIG. 3 to its position shown in FIG. 4.

The actuation of the trigger 112 will move the slidable actuating member126 to the left so that the end thereof will raise the pawl 1 30 onwhich the strap adjuster 140 is positioned into the position shown inFIG. 4. This permits the end of the strap adjuster 140 to come intoengagement with the helical groove positioned in the cylindrical guide38.

A suitable power means drives the drive cable 66 thereby driving theinterconnecting cable 56 through the drive mechanism 58. As viewed fromthe end of the tool 10 having the drive cable 66, the direction ofrotation of the drive cable 66 is clockwise. By way of amplification,the clockwise rotation of the cable 66 is transmitted to the drivesleeve 62 by the enlarged end 68. This rotation is transmitted to theplunger 78, more particularly, the main body portion 84 thereof, bymeans of the pin 96 which is urged into the ends of helical grooves 88and by the spring 74 acting on the plunger 78 through ball 76. Therotation is then transmitted to the interconnecting cable 56 via pin 98positioned in engagement with the differential housing 89 through thesides of the longitudinal slots 92 and 94. The rotation of theinterconnecting cable 56 will in turn rotate the worm 52 therebyrotating the gear 36, the serrated roller 34 and the cylindrical guidemember 38. If there is any misalignment of the end 30 of the strap 26,the strap adjuster 140 will move inwardly toward the serrated roller 32in a direction parallel to the axis of the helical grooved guide 36since the end of the strap adjuster 140 has been positioned in thehelical grooves when the pawl was raised by actuation of the trigger112. This action will move the end of the strap or tie, as shown in FIG.8, into the proper position where it can be engaged by the serratedroller 32. The serrated portion 134 of the pawl 130 will engage thestrap so that the serrated roller 32 will properly grip the strap end 30and this motion will continue to rotate the pawl 130 in acounterclockwise direction, as viewed in FIGS. 3 and 4, to the positionwhere the smooth curved portion 136 will come into engagement with thestrap and hold it in engagement with the serrated roller 32. This smoothportion permits the strap to slide over it as the serrated roller 32begins to tension the strap or tie 26.

The head 24 of the strap 26 is then positioned in engagement with theoval or oblong indentation 122 in the end 16 of front housing portion 13thereby preventing the head 24 from rotating during subsequent twistingand cutting operations.

As strap 26 begins to be tightly drawn around the parallel extendingconductors or wires 28, the turning force necessary to turn the serratedroller 32, the gear 36 and the worm 52 will increase thereby increasingthe rotary force that must be present to drive these three components atthe interconnecting cable 56 and at the differential housing 89. Whenthe strap 26 begins to be tensioned around the parallel extendingconductors or wires 28, it can be appreciated that the rate of rotationof the serrated roller 32, the gear 36, the worm 52, the interconnectingcable 56 and the differential housing 89 will be substantially reduced.The driving cable 66, however, will continue to be rotated in aclockwise direction as the tool is viewed from the end where this cableis connected. This continued rotation will cause the inner plungermember 78 to be rotated in a counterclockwise direction as viewed fromthe end of the tool to which the cable 66 is attached relative to theextension 80 of the drive sleeve 62. This action is permitted by thecooperation of the helical grooves 88 and 90 positioned in the extension80 and the pin 96 atiixed to the main body portion 84 of the plunger 78.This action forces the plunger 78 to the right as viewed in FIG. 3 intothe position shown in FIG. 5 and the pin 98 attached to the main bodyportion 84 of the plunger 78 is permitted to slide longitudinally withrespect to the axis of the plunger 78 through the slots 92 and 94positioned in the ditferential housing 89.

The movement of the plunger 78 to the right against the bias of thespring 74 causes the conical ramp surface 86 to force the balls 102 ofthe clutch 60 radially outwardly into engagement with the clutch member103 attached to the rotatable cylinder or barrel 44 thereby applying arotating force on the cylinder or barrel which tends to rotate itclockwise as viewed from the end of the tool having the driving cable66.

It will be remembered, however, that the pin 172 supported by themovable plunger 152 mounted in the bore 150 in the handle 14 has rollers174 mounted thereon that are in engagement with the walls of a helicalgroove 176 positioned in the rotatable cylinder. This pin in cooperationwith the helical groove 176 as positioned in FIG. 9, will preventrotation of the rotatable cylinder 44 until sufficient force has beenapplied to it to overcome the force of the spring 164 that urges theball 162 into engagement with the indented portion 160 of the plunger152. As stated previously, the compressive force of the spring 164 onthe ball 162 may be varied by the adjustment of the adjusting screw 170.When the force of this spring 164 is overcome, however, by sufficientforce being applied to the plunger 152 along a line parallel to its axisthrough the pin 172 and the edge of the helical groove 176, the ball 162will move downwardly, as viewed in FIG. 3. This permits the force beingapplied on the rotatable cylinder 44 to move the plunger 152 to theright, as viewed in FIG. 3, into the position as viewed in FIG. 5through the action of the helical groove 176 and the pin 172 as thecylinder 44 rotates.

It should be understood that the ball 162 when forced into the indentedportion 160 of the plunger 152 by the spring 164 prevents rotation ofthe cylinder 44 due to the friction between the pawl 130 and the strap26 until sufficient force has been applied to overcome the compressivestrength of the spring 164. This force will be supplied as soon as theclutch 60 becomes engaged by the above-described action upon apredetermined tension existing in the strap 26.

The rotation of the cylinder 44 will rotate the rotatable support member42 from the position shown in FIGS. 1 and 3 into the position shown inFIG. 5, thereby imparting a twist in the end 30 of the strap 26 at thepoint shown in FIG. 5. As shown in the drawings, the direction iscounterclockwise, as viewed in FIGS. 10 through 12 and clockwise asviewed from the end of the tool that has the driving cable 66, and theangle is approximately but any other suitable angle could be employed.

The continuing rotation of the rotatable support member 42 brings theshearing knife 192 shown in FIG. 11, into play and it will come intoabutment with a shoulder formed in the front housing portion 13, asshown in FIG. 12, thereby applying a rotating force on the shearingknife 192 that rotates it with respect to the rotatable support member42 and moves its cutting edge through the end 30 of the strap or tie 26.

It can be appreciated therefore that the twisting and cutting of thestrap 26 occurs when the clutch mechanism 60 is actuated against thebias of spring 74 when a predetermined tension level occurs in the strap26 and that this level may be set by the adjustment of adjusting plug72.

As shown in the drawings, the strap 26 is constructed of a plasticmaterial that will take a permanent set as the twisting operation occursso that when the end 30 is cut by the shearing knife 192, the twist willremain. The strap 26 therefore will be under a permanent tension aroundthe parallel extending conductors or wires 28. The end 30 with the twistin it cannot therefore move back through the horizontal slot in the head24, The continued rotation of the gear 36 and serrated roller 32 as theend 39 of the strap is severed will short the severed end of the strapout of the tool.

When the forces in the drive mechanism 58 are released by the severingof the end 30 of the strap or tie 26 by the shearing knife 192, thespring 74 will force the plunger to the left from the position shown inFIG. 5 to the position shown in FIG. 3 thereby disengaging the clutch60. The return spring 154 that is in engagement with the plunger 152will move the plunger to the left from its position shown in FIG. 5 tothe positions shown in FIGS. 3 and 4. The pin 1.72 with its rollers 174positioned in the helical groove 176 in the rotatable cylinder 44 willtherefore rotate the cylinder 44 and the rotatable support member 42back into the position shown in FIGS. 3 and 4. The operator will thenrelease the trigger 112 and the tool will then be in position to performanother tying operation.

It should be noted that the twisting and cutting operations on the strap26 occur automatically upon a predetermined tension occurring in thestrap and that this predetermined tension may be set by the adjustmentof the adjusting screw 72 that adjusts the force applied by the spring74 against the plunger 78.

The present invention thus provides a compact, efficient and easilyoperated power tool for placing a strap around a group of parallelextending wires, conductors or the like in which the strap will beautomatically twisted and thereafter cut when a predetermined tension ispresent in the strap. This twisting and cutting operation leaves thestrap under this'predetermined tension around the parallel extendinggroup of wires, conductors or the like, to bind them together in theform of a simulated cable Although a preferred embodiment of theinvention has been illustrated and described in detail, it should beunder stood that various modifications and additions may be made theretowithout departing from the scope of the invention as defined in thefollowing claims.

What is claimed is:

1. A power operated tool for tensioning a strap comprising means forrestraining movement of one end of the strap, rotary means for grippingthe strap in a location spaced from said one end, manually operablemeans for biasing a strap into engagement with said second mentionedmeans, power operated means coupled to said second mentioned means anddriving said second mentioned means in rotation for tensioning thestrap, and means responsive to a predetermined tension in the strap fortwisting the portion of the strap held by said second mentioned means toimpart a permanent twist in said strap.

2. The combination of claim 1 includes a shearing means operativelycoupled to one of said first or second mentioned means for shearing theportion of the strap on the opposite side of the permanent twist fromsaid first mentioned means as said last mentioned means continues totwist the strap.

3. The combination of claim 1 including means operatively coupled tosaid second mentioned means and said last mentioned means for rotatingsaid second mentioned means through a substantial angle upon theoccurrence of the predetermined tension in the strap.

4. The combination of claim 3 in which said second mentioned meanscomprises a serrated roller mounted in said power operated tool on arotatable axis substantially perpendicular to the motion of the strap asit is tensioned.

5. The combination of claim 4 in which said serrated roller is supportedin a rotatable support means rotatably supported in said power-operatedtool about an axis substantially perpendicular to the axis of saidroller.

6. The combination of claim 5 in which said poweroperated meanscomprises a drive means positioned in said rotatable support means, saiddrive means including a clutch having means operable upon apredetermined tension in the strap for engaging the clutch with saidrotatable support means thereby rotating said rotatable support memberand said serrated roller through said substantial angle.

7. The combination of claim 6 in which a spring urged means carried bysaid power tool engages said rotatable support means for preventing saidclutch means from rotating said rotatable su port means prior to thetime when said predetermined tension is present in said strap.

8. The combination of claim 5 including a trigger means carried by saidpower-operated tool, a pivotally mounted pawl pivotally mounted in saidrotatable support member adjacent said serrated roller, and meansinterconnecting said trigger means and said pivotally mounted pawl forpivoting said pawl upon the actuation of said trigger means, said pawlengaging the strap upon pivotal movement thereof for bringing it intoengagement with said serrated roller.

9. The combination of claim 8 including a strap posi tioning meanscarried by said pawl, and means rotatable with said serrated rollerengaging said strap positioning means when said pivotally mounted pawlis rotated by the actuation of said trigger means said strap positioningmeans including means for moving said strap into engagement With saidserrated roller and said pawl.

10. The combination of claim 2 including means operatively coupled tosaid second mentioned means and said last mentioned means for rotatingsaid second mentioned means through a substantial angle upon theoccurrence of the predetermined tension in the strap.

11. The combination of claim 10 in which said second mentioned meanscomprises a serrated roller mounted in said power operated tool on arotatable axis substantially perpendicular to the motion of the strap asit is tensioned.

12. The combination of claim 11 in which said serrated roller issupported in a rotatable support means rotatably supported in said poweroperated tool about an axis substantially perpendicular to the axis ofsaid roller.

13. The combination of claim 12 in which said poweroperated meanscomprises a drive means positioned in said rotatable support means, saiddrive means including a clutch having means operable upon apredetermined tension in the strap for engaging the clutch with saidrotatable support means thereby rotating said rotatable support memberand said serrated roller through said substantial angle.

14. The combination of claim 13 in which a springurged means carried bysaid power tool engages said rotatable support means for preventingrotation of said rotatable support means prior to the time said clutchis engaged due to said predetermined tension in said strap.

15. The combination of claim 12 including a trigger means carried bysaid power-operated tool, a pivotally mounted pawl pivotally mounted insaid rotatable support member adjacent said serrated roller, and meansinterconnectin said trigger means and said pivotally mounted pawl forpivoting said pawl upon the actuation of said trigger means, said pawlengaging the strap upon pivotal movement thereof for bringing it intoengagem nt with said serrated roller.

16. The combination of claim 15 including a strap positioning meanscarried by said pawl, and means rotatable with said serrated rollerengaging said strap positioning means when said pivotally mounted pawlis rotated by the actuation of said trigger means, said strappositioning means including means for moving said strap into engagementwith said serrated roller and said pawl.

17. In a power-operated tool for tensioning a strap around a pluralityof parallel extending wires, conductors or the like, with the strapincluding an enlarged end having a rectangular aperture positionedtherein, and a complementary shaped rectangular main body portioncomprising a housing having an end portion, means on said end portionholding said enlarged end of the strap for preventing. rotation thereof,a support means'rotatably mounted in said housing, a serrated rollerrotatably mounted in said rotatable support member about an axissubstantially perpendicular to the axis of rotation of said supportmember, cooperating means mounted in said support member for causing themain body portion of the strap to be brought into engagement with saidserrated roller, a drive means mounted in said support member fordriving said serrated roller, and means cou pled to and operated by saiddrive means for imparting a rotary force on said support member when thetension in said strap reaches a predetermined level, whereby when saidpredetermined tension occurs in the strap, said rotatable support memberincluding said serrated roller is rotated about an axis substantiallyperpendicular to the axis of rotation of said roller and a twist isimparted to the main body portion of the strap.

18. The combination of claim 17 including cutting means carried by saidrotatable support member for cutting the main body portion of the strapwhen the rotatable support means has been rotated through an anglesuflicient to impart the twist to the strap.

19. The combination of claim 18 including means carried by saidpower-operated tool and engaging said rotatable support means forpreventnig rotation of said rotatable support means prior to the timesaid predetermined tension occurs in said strap.

21 The combination of claim 18 in which said means coupled to andoperated by said drive means for imparting a rotary force on saidsupport member comprises a clutch having clutching members carried bysaid drive means, and means carried by said drive means for forcing saidclutching members into engagement with said rotatable support memberwhen said predetermined tension occurs in the strap.

21. The combination of claim 19 in which said means carried by saidpower-operated tool and engaging said rotatable support means forpreventing rotation of said rotatable support means until saidpredetermined tension occurs in said strap comprises a spring-urgedplunger mounted in said power tool for reciprocal movement in adirection substantially parallel to the axis of rotation of said supportmember, a pin carried by said plunger, said rotatable support memberhaving a helical groove for the reception of said pin, and ball detentmeans positioned in said power tool and engaging said plunger.

References Cited UNITED STATES PATENTS 3,173,456 3/1965 Bailey 140149 106/1966 Caveney et al. 140123.6 7/1967 Lawson et a1 14093.2

US. Cl. X.R.

